Virtual distributed security system

ABSTRACT

A distributed security system is provided. The distributed security system uses a security policy that is written in a policy language that is transport and security protocol independent as well as independent of cryptographic technologies. This security policy can be expressed using the language to create different security components allowing for greater scalability and flexibility. By abstracting underlying protocols and technologies, multiple environments and platforms can be supported.

This application is a divisional of U.S. patent application Ser. No.10/068,444, filed Feb. 6, 2002 which relates to and claims priority fromU.S. Provisional Application No. 60/329,796, filed Oct. 16, 2001, andU.S. Provisional Application No. 60/346,370, filed Oct. 19, 2001, eachof which is herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of computer security systems.More particularly, the invention provides methods and devices forproviding security to distributed computer systems.

2. Description of Related Art

Security frameworks have been developed to protect data transmitted indistributed computing systems. Existing security frameworks have anassortment of degrees of privacy, security, adaptability andscalability. The Kerberos system, for example, provides securecommunications by users sharing a key with a third party. In order toconduct secure communications, each party connect to the third party andutilize the key issued by the third party. Among other disadvantages,the Kerberos system allows the third party to track the identities ofusers who are communicating with each. Furthermore, the third party hasthe ability to decrypt messages because the third party issues the keys.The Kerberos security model is fixed; that is, administrators havelimited flexibility in deployment options.

Other existing security systems have merits and limitations. Forexample, security systems that utilize public key and private keyinfrastructures can include time-consuming and expensive encryption anddecryption steps. Time consuming encryption and decryption steps canlimit the scalability of a security system if they are performed toofrequently. As well, PKI infrastructures often have revocation issuesand many don't address the issue of management of multiple trust rootsor cross-certification. Most solutions are designed for specificpurposes, e.g., SSL or IPsec. Existing security systems have alsogenerally focused on specific cryptographic technologies. For example,Kerberos uses symmetric keys and PKI uses public keys.

There exists a need in the art for a generic security framework, for usewith distributed computing systems, that is security protocolindependent and that can be scaled for use with wide area networks, suchas the Internet, and that is independent of the underlying cryptographicmechanisms being used.

BRIEF SUMMARY OF THE INVENTION

The present invention overcomes one or more problems and limitations ofthe prior art by providing a generic security framework that istransport and security protocol independent and that can supportmultiple cryptographic technologies. The security framework utilizes asecurity policy which may describe the components of the framework,their properties, capabilities, requirements, and interactions. Thepolicy is expressed using a security policy language. The securitypolicy language allows different security components to be defined andconfigured without changing application code. Using this mechanism, aspecific set of security services can be defined which meet the needs ofa specific deployment. Furthermore, the security components allow thesecurity services to be partitioned to increase both flexibility andscalability. By capturing the security semantics within a language, theunderlying implementation is abstract thereby creating a “virtualdistributed security system.” Furthermore, with the security semanticsexpressed in language, the underlying protocols are abstracted allowingthe security runtime to support different platforms, technologies, andprotocols. Finally, with a security policy definition in language form,it is possible to construct proofs of the security system.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and not limitedin the accompanying figures in which like reference numerals indicatesimilar elements and in which:

FIG. 1 illustrates an exemplary distributed computing system operatingenvironment;

FIG. 2 illustrates an architecture of a virtual distributed securitysystem, in accordance with an embodiment of the invention;

FIG. 3 illustrates a sample set of security components that may bedefined by a security policy, in accordance with an embodiment of theinvention;

FIG. 4 illustrates a license directory, in accordance with an embodimentof the invention;

FIG. 5 shows a method that may be used by a directory to verify thestatus of licenses, in accordance with an embodiment of the invention;

FIG. 6 illustrates how an application using a virtual distributedsecurity system can communicate with an existing security component, inaccordance with an embodiment of the invention;

FIG. 7 illustrates elements of a security policy that may be utilizedfor permission processing, in accordance with an embodiment of theinvention;

FIG. 8 illustrates a security policy, in accordance with an embodimentof the invention;

FIG. 9 illustrates a security policy that specifies how to partitionservice components, in accordance with an embodiment of the invention;

FIG. 10 illustrates a security policy that specifies how partitionedservice components maybe deployed to systems, in accordance with anembodiment of the invention; and

FIG. 11 illustrates a method of sending secure messages in accordancewith an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Aspects of the present invention are suitable for use in a variety ofdistributed computing system environments. In distributed computingenvironments, tasks may be performed by remote computer devices that arelinked through communications networks. Embodiments of the presentinvention may comprise special purpose and/or general purpose computerdevices that each may include standard computer hardware such as acentral processing unit (CPU) or other processing means for executingcomputer executable instructions, computer readable media for storingexecutable instructions, a display or other output means for displayingor outputting information, a keyboard or other input means for inputtinginformation, and so forth. Examples of suitable computer devices includehand-held devices, multiprocessor systems, microprocessor-based orprogrammable consumer electronics, network PCS, minicomputers, mainframecomputers, and the like.

The invention will be described in the general context ofcomputer-executable instructions, such as program modules, that areexecuted by a personal computer or a server. Generally, program modulesinclude routines, programs, objects, components, data structures, etc.,that perform particular tasks or implement particular abstract datatypes. Typically the functionality of the program modules may becombined or distributed as desired in various environments.

Embodiments within the scope of the present invention also includecomputer readable media having executable instructions. Such computerreadable media can be any available media which can be accessed by ageneral purpose or special purpose computer. By way of example, and notlimitation, such computer readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium which can be used to storethe desired executable instructions and which can be accessed by ageneral purpose or special purpose computer. Combinations of the aboveshould also be included within the scope of computer readable media.Executable instructions comprise, for example, instructions and datawhich cause a general purpose computer, special purpose computer, orspecial purpose processing device to perform a certain function or groupof functions.

FIG. 1 illustrates an example of a suitable distributed computing system100 operating environment in which the invention may be implemented.Distributed computing system 100 is only one example of a suitableoperating environment and is not intended to suggest any limitation asto the scope of use or functionality of the invention. System 100 isshown as including a communications network 102. The specific networkimplementation used can be comprised of, for example, any type of localarea network (LAN) and associated LAN topologies and protocols; simplepoint-to-point networks (such as direct modem-to-modem connection); andwide area network (WAN) implementations, including public Internets andcommercial based network services such as Microsoft7 Network. Systemsmay also include more than one communication network, such as a LANcoupled to the Internet

Computer device 104, computer device 106 and computer device 108 may becoupled to communications network 102 through communication devices.Network interfaces or adapters may be used to connect computer devices104, 106 and 108 to a LAN. When communications network 102 includes aWAN, modems or other means for establishing a communications over WANsmay be utilized. Computer devices 104, 106 and 108 may communicate withone another via communication network 102 in ways that are well known inthe art. The existence of any of various well-known protocols, such asTCP/IP, Ethernet, FTP, HTTP and the like, is presumed.

Computers devices 104, 106 and 108 may exchange content, applications,messages and other objects via communications network 102. In someaspects of the invention, computer device 108 may be implemented with aserver computer or server farm. Computer device 108 may also beconfigured to provide services to computer devices 104 and 106.

FIG. 2 illustrates an architecture of a virtual distributed securitysystem in accordance with an embodiment of the invention. Applications202 a, 202 b, and 202 c use a virtual distributed security system 204for security-related operations. Virtual distributed security systems204 may use one or more security policies 210 a-210 c (for establishingsecurity rules and procedures and implement the security policy with oneor more protocols 206 a-206 c and transports 206 a-206 c). In oneembodiment of the invention, applications 202 a, 202 b and 202 c orother entities may negotiate over the use of a security policy. Inparticular, the entities may exchange messages to negotiate overportions of security polices 210 a-210 c to use as a custom securitypolicy. Security policies 210 a-210 c are described in detail below andbe written in a common or different security policy language. In oneembodiment, virtual distributed security system 204 is implemented witha set of application programming interfaces (APIs). However, thoseskilled in the art recognize that there are many alternative mechanismsfor implementing virtual distributed security system 204. For example,in other embodiments virtual distributed security system 204 could befully distributed and/or implemented with a set of services. In yetanother embodiment virtual distributed security system 204 could beimplemented with a set of Java beans or other Java language derivative.

Security policies 210 a-210 c may describe the behaviors of componentsof a system or an overall security semantics of a system. For example,when sending a message, a security policy may require that the messagebe signed in a specific way or that mutiple signatures of specific formsmust be present, that certain credentials must be presented and that atleast a portion of the message is encrypted. In another example, asecurity policy may identify the steps that must be taken beforeaccessing a service.

The security policy may be authored by a system administrator or anapplication developers. Instead of a limited number of access controlrules like prior art methods, aspects of the present invention allowusers and applications to create new access and other rules by creatingor modifying a security policy. For example, for a particular service,an adminstrator may want users to have a special read access. In priorart systems, the rights that may be utilized are hard coded within thesecurity system. For example, Windows NT operating systems has 32defined permission rights. With the present invention, the administratorcan define new rights by defining or editing a security policy. Thesecuirty policy may be capability based, i.e, an application may definea capability and virtual distributed security system 202 may providethat capability.

Security policies 210 a-210 c may be authored in a security policylanguage. The security policy language may be used to describe thesecurity components, their properties, capabilities, requirements,interaction semantics and other security aspects. Those skilled in theart will appreciate that such a language could be expressed in manydifferent forms. In some embodiments, the security language may be alogic-based language, such as Prolog or some derivative. In otherembodiments, the security language may be rule-based or a proceduralbased. Of course, the security language may also be any combination oflogic-based, rule based or procedural based. In one embodiment, securitypolicies 210 a-210 c are implemented with extensible markup language(XML) documents.

FIG. 3 illustrates a sample set of security components 306 a-306 i thatmay be defined by a security policy. Security components 306 a-306 i maybe implemented with library routines, separate services, or othermechanisms. An application 302 is interacting with a service 304.Security components 306 a-306 i provide a security environment for thiscommunication.

An identity component 306 a may provide a mechanism to authenticate aprincipal and provide authoritative proof of the identity. Proof of anidentity may be established with a credential, ticket, license, or someother mechanism acceptable to identity component 306 a. Aspects of thepresent invention are described below with respect to licenses. Alicense contains a set of assertions and is signed by an authority. Oneskilled in the art will appreciate that in alternative embodiments,credentials, tickets or other mechanisms may be utilized.

An admission component 306 b may provide a mechanism for regulatingaccess to a trust domain of service 304. Admission component 306 b maymap external credentials to internal credentials. For example,application 302 may provide public key credentials to admissioncomponent 306 b, and admission component 306 b may return symmetric keycredentials to application 302.

A permission component 306 c may provide a mechanism for pre-fetchingrights, capabilities, or other access control information. Permissioncomponent 306 c allows service 304 to compare signed credentialsreceived from permission component 306 c with the requiredrights/capabilities for the operation requested by application 302.Comparing rights is generally more efficient for service 304 than“fetching” rights, particularly in embodiments where rights do notchange.

A shared key component 306 d may provide a mechanism to securely sharesecrets between service 304, security components 306, and other servicesthat exist within a trust domain of service 304. For example, if theadmission service 306 b returned a symmetric key license, it may beencoded using a shared key for the trust domain. Service 304 can obtainthe shared key used by admission service 306 b from shared key service306 d and use the shared key to decode the license.

A revocation component 306 e may provide a mechanism for trackingrevocation. For example, credentials issued outside the trust domainmight be monitored for revocation, for example, using certificaterevocation lists (CRLS). Revocation component 306 e may also monitorusage within the trust domain and revoke credentials, tickets, licenses,or other mechanisms that are being misused. For example, anadministrator can set limits on licenses for application 302 such ascall limits, time limits, or frequency limits. A call limit may limitthe number of times a license may be utilized. A time limit may limit alicense to a specific time period and a frequency limit may limit thenumber of times a license can be utilized within a given time period. Ifapplication 302 exceeds these limits, the license can be revoked. Whencoupled with a metering system, this provides a mechanism to limit theexposure of a denial of service attack, especially if it is accidental.This mechanism is also important when dealing with server farms. Inprior art systems, limits are typically divided by the number of serversand allocated accordingly. For example, if there are 10 servers andthere is a call limit of 20, each individual server will have a calllimit of 2. In other prior art systems, the call limit is applied toeach server. As a result, with 10 servers and a call limit of 20, theactual call limit can be 200. Revocation component 306 e may track theactivity of all of the servers and ensure that the call limit is notexceeded. Of course, propagation delays between servers and revocationcomponent 306 e or a metering system may cause a call limit to beslightly exceeded in some cases.

A trust component 306 f may provide a mechanism for managing trustrelationships. Trust component 306 f may utilize a trust policy or truststatement to indicate how an entity is trusted and/or the extent towhich an entity is trusted. A trust relationship allows a first entityto trust a second entity when the first entity trusts an authority thatissues a license to the second entity. In some embodiments, entities maydefine the scope of the trust. For example, a first entity may trust asecond entity for transactions with certain URLs. Trust relationshipsmay contain a cryptographic component. For example, with public keysembodiments, certification chains are processed and, eventually, acertificate may be signed by a trusted authority. This mechanismmaintains the trusted identities and their certificates so that theycannot be altered without proper authorization. Similarly, a party maynot trust the root of another party's certificate, but may countersignor trust a countersignature on the certificate (cross certification). Inmany circumstances trusts may be shared across different applicationsand services or even instances (e.g. farms) of a service. In such anenvironment trust component 306 f provides a mechanism for the trustingparties to be notified or obtain updates including additions, changes,or deletions of trusted parties. Those skilled in the art recognize thatthere can be multiple mechanisms for distributing updates, including,but not limited to, polling and eventing and a security policy may makeselections among the available options.

Trust component 306 f may provide a trust mechanism that spansenterprises or organizations. For example, application 302 may work withservice 304 in a specific contract to deal with parts ordering andtracking. While application 302 and service 304 may be running atdifferent companies, application 302 and service 304 may both alsointeract another entity, such as a parts company. Application 302 andservice 304 may both choose to trust any entity that the parts companyspecifies as trusted (e.g. its sub-contractors).

A store component 306 g may provide a mechanism for storing, retrieving,encrypting and managing credentials, such as licenses. Store component306 g may be used as a lockbox (personal storage), a directory, aregistry, an escrow or other storage mechanism. Furthermore, storecomponent 306 g can verify the stored licenses, including periodicrevocation checks and countersign the credentials allowing parties thattrust store component 306 g to optimize processing and skip validationchecks.

In one embodiment, the functionality of store component 306 g may beimplemented with a directory, such as directory 402 shown in FIG. 4. Theowners of licenses may retrieve and use the licenses as they are needed.Directory 402 includes a memory module 404 for storing a plurality oflicenses. Memory module 404 is shown with three licenses 406, 410 and414 belonging to a consumer A for illustration purposes only. Moreover,while licenses are shown, one skilled in the art will appreciate thatother credentials, such as private keys may be utilized. Memory module404 may contain licenses belonging to any number of entities and issuedby any number of authorities. License 406 was issued by an authority408, license 410 was issued by an authority 412 and license 414 wasissued by an authority 416.

Directory 402 may also include a processor 418 and a verification module420 that can be used to verify the status of one or more licenses storedin memory module 404. FIG. 5 illustrates an exemplary method thatprocessor 418 and verification module 420 may use to verify the statusof a license. In step 502, directory 402 stores in a memory at least onelicense issued by an authority to a license owner. License 406, forexample, was issued by authority 408 and is stored in memory module 404.Next, in step 504, directory 402 periodically transmits anidentification message of the license to the authority. The directorymay be configured to transmit identification messages hourly, daily,weekly or at any other interval. In one embodiment of the invention, theinterval is determined by the authority that issued the license. Forexample, an authority may desire to have updates more frequently formore sensitive licenses. The identification messages may include alicense identification number, e.g., “156DVX22” for license 406. Theauthority may use the license identification number to determine whetherthe license has been revoked, replaced or modified. In an alternativeembodiment, one or more authorities periodically transmit statusmessages to directory 402 without first receiving an identificationmessage. For example, an authority may send a status message to adirectory when the status of a license has changed. Polling andsynchronization may be used when an entity has been disconnected oroffline.

In step 506, the directory receives, from the authority, at least onestatus message indicating the status of the license. The status messagemay indicate that the license remains valid, has been revoked, has beenmodified or some other status. In step 508, it is determined whether thestatus message includes instructions for modifying the license. If thestatus message includes modification instructions, the license ismodified in step 510. A license may be modified by expanding or limitingits scope or duration or modifying any assertion or condition. Next, instep 512, it is determined whether the license includes instructions fordeleting the license. A license may be deleted when it has been revokedby the issuing authority. If the status message indicates that thelicense is to be deleted, the license is deleted in step 514.

Directory 402 may receive, from the license owner, a request for thelicense in step 516. The license owner may request the license when thelicense owner desires to use the license, for example. When the issuingauthority has not revoked the license, directory 402 may transmit thelicense to the license owner in step 518.

Returning to FIG. 3, an integrity component 306 h may provide mechanismsfor signing (digitally) portions of a message and verifying integrityand signatures of received messages in accordance with securitypolicies. A confidentiality component 306 i may provide mechanisms forencrypting and decrypting portions of a message. One skilled in the artwill appreciate that there are many mechanisms that may be used toimplement integrity component 306 h and confidentiality component 306 iand that in some embodiments a security policy makes a selection fromthe available options.

One of the advantages of abstracting underlying protocols and transportsis that abstraction facilitates interoperability with other systems.FIG. 6 illustrates how an application 602 using a virtual distributedsecurity system 604 can communicate with an existing security component606. Interoperability can occur because virtual distributed security 602may select the most appropriate protocol 610 and transport 612 based oninformation included in a security policy 608. In one aspect of theinvention, protocol 610 may be a composable protocol. Virtualdistributed security system 604 may be built as a set of services withan application programming interface (API) that application 602 mayutilize. The API allows application 602 and system virtual distributedsecurity system 604 to communicate with one another through a variety ofdifferent mechanisms such as, but not restricted to RPC, SOAP, or sharedmemory.

FIG. 7 illustrates elements of a security policy 700 that may beutilized for permission processing. Policy 700 may define the securityrights 702 associated with each service 704 and the mappings of rightsto identities 706. Such mappings could be based on many criteriaincluding, but not limited to, name, authority, credential type,associated group, or associated roles. Policy 700 may also definedifferent messages 704 a-704 c that a service 704 receives andrequirements 708 of each of messages 704 a-704 c. For example, one ormore credential, integrity, confidentiality or right requirements mayvary by message. That is, it may be required that a message is signed orencrypted, and it may indicate the supported/required algorithms to use.Policy 700 illustrates an example in which an XML license is requiredfrom an admission component 710. Additionally, a requirement may specifywhich application protocol elements must be signed and those applicationprotocol elements that are required for a message.

A policy language used to create a security policy may define thefunctionality of a component using security primitives. The securityprimitives may be in combination with traditional programming elements.Those skilled in the art will recognize that security primitives cantake various forms. In one embodiment, the primitives might behigh-level constructs like “create a license” or “manage storage of alicense” which are controlled by the use of parameters. For example thepolicy 802, shown in FIG. 8, for an admission component 804 mightrepresent “create a license of type X for name N using key Y signed bylicense L.” In another embodiment, the primitives might be verylow-level constructs such as “fetch the template for type X; replace the‘name’ with N; set the ‘date’ field to ‘10/24/2001’, set the ‘authority’field to Z; set the ‘key’ field to Y; sign fields ‘name’, ‘date’,‘authority’, and ‘key’ with license L using algorithm Y”. Of course,other embodiments of the invention may combine different levels ofconstructs.

Security policies, such as security policy 802 allow a definition of adistributed security system without the writing of code. Among otheradvantages, a security system that does not require the writing andrewriting of code allows for custom components to be inserted to augmentor replace specific steps. Such components could be provided by, but notlimited to, native processor code, Java beans or other Java languagederivatives, or Microsoft CLR modules.

In one aspect of the invention, each security module may be describedindependently and a security policy can then indicate how to combinemodules, and, how to deploy modules. Such information may be part of thepolicy, or part of an independent deployment mechanism. Providingflexibility in describing, combining and deploying modules allows adistributed security system to support partitioning, replication, andfarming. For example, in FIG. 9, policy 902 might specify how topartition service components 904 a-904 g into separate partitions 906a-906 c. Those skilled in the art will appreciate that in addition tosecurity related services, the teachings shown in FIG. 9 may be appliedto non-security related services.

Similarly, a policy, such as policy 1000 shown in FIG. 10 might furtherspecify which partitions 1002 a-1002 are deployed to systems 1004 a-1004f in a distributed computing systems. Systems 1004 a-1004 f may beimplemented with applications, computing devices, separate processors ofa multiprocessor system or other hardware or software. As is shown inFIG. 10, a single partition may be present on more than one system ofthe distributed computing system.

A distributed security system may abstract cryptographic objects andoperations to make the system independent of the underlyingcryptographic technology. Licenses have been described above and may bea credential that is given to another party to identify oneself.Examples of licenses include X.509 certificates and Kerberos tickets. A“testament” may be proof that a party uses to prove that they own alicense or a key within the license. For example, an X.509 certificatecontains a public key and a corresponding testament may be theassociated private key. Similarly, a Kerberos ticket includes anencrypted symmetric key and the testament may be the symmetric keyitself.

A security policy may utilize elements such as licenses and testamentsto create a single programming model for securing messages usingoperations such as sign, verify, encrypt, and decrypt. To sign amessage, the license owner, for example, may encrypt a digest of themessage with their testament. The holder of a license may verify thesignature. Similarly, to encrypt a message, an entity may use a key inthe recipient's license. The recipient may decrypt the message using atestament belonging to the recipient. In embodiments that utilize publickeys, a message may be encrypted with a generated symmetric key and thesymmetric key may be encrypted with a public key from the license.

FIG. 11 illustrates an example in which an entity 1102 sends a message1104 to another entity 1106. Entity 1102 owns a license 1108 and atestament 1110. Similarly, entity 1106 owns a license 1112 and atestament 1114. Entities 1102 and 1106 wish for message 1104 to besecure. Entity 1102 initiates a sign operation 1116 on message 1104 bycomputing a digest of message 1104 and then encrypting the digest withits testament 1110. Next, entity 1102 may perform an encrypt operation1124. Entity 1102 may create a key 1118 and encrypt message 1104 withkey 1118. Key 1118 may then be encrypted using license 1112, whichbelongs to entity 1106. The encryption of key 1118 may involveencrypting key 1118 with a key found in license 1112. The encryptedmessage, the encrypted key, and the signature are transmitted to entity1106. In other embodiments of the invention, credentials other than keysmay be utilized.

Entity 1106 can perform a decrypt operation 1120 to decrypt key 1118using its testament 1114. Using key 1118, entity 1106 can decryptmessage 1104. Next, entity 1106 may perform a verify operation 1122.Entity 1106 may compute a digest of message 1104 and compare thecomputed digest with the digest sent by entity 1102 using license 1108.

One of the advantages of the present invention is that applicationsrunning for entities 1102 and 1106 may be the same, regardless ofwhether licenses 1108 and 1112 contain public keys, symmetric keys,digest keys, or other forms of credentials. The specifics of thecryptographic algorithms may be handled by the security system, not theapplication. Handling cryptographic algorithms with a security systemsis particularly desirable when heterogeneous credentials are used. Thatis, licenses 1108 and 1112 use different cryptographic techniques. Intraditional systems, applications must be aware of this and be codedspecifically for the presence of diverse cryptographic techniques. Thepresent invention abstracts cryptographic techniques and does notrequire applications to be aware of the cryptographic technologies beingused. As a result, cryptographic techniques can be altered at any timesimply by altering a security policy.

The disclosed security model can be used to create richer environments.For example, while describing FIG. 3, it was indicated that admissioncomponent 306 b might accept public key credentials and generatesymmetric key licenses. The logic in admission component 306 b or in anyother service may be the same regardless of the type of license used.With such a service, the services can have increased scalability bysimply using a symmetric key license. The operation of receiving alicense and then issuing another license is defined as a re-issuanceoperation because component 306 b is “re-issuing” the sender's licenseusing its own format. In some cases, component 306 b, or a similarcomponent, might return a license with the same key. For example,component 306 b may accept an X.509 certificate, but return an XMLlicense with the same public key because component 306 c only acceptsXML licenses.

Re-issuance may form the basis of a delegation operation. A party A maymake a specific delegation to another party B. To do this, A mayre-issues B's license specifying the delegations (as well as anyconditions) and sign the license as the issuing authority. To use thisnew license, B may be required to present the license, proof ofownership (e.g. a signature), and A's license (if the recipient doesn'thave it). The recipient may then verify that B owns the license and theA issued it, and that the delegations in the license correctlycorrespond to A's license. The abstraction of cryptographic technologiesand, specific license formats, allows applications to use a consistentprogramming model independent of the cryptographic technologies orlicense formats used at any specific time.

Another use of licenses and key abstraction is service scalability.Existing systems are typically limited when creating special keys forcommunications because only the client and the service know the key andstate on the service limits scalability. The existing approach haslimitations when a service is implemented as part of a server farm.Aspects of the present invention allow the service to re-issue thesender's license providing a session key, but encrypting it with asecret key that is shared across the farm, possibly using the shared keyservice 306 d. Consequently, any server in the farm that receives amessage can understand and process the message since it can abstract thesession key, and no state is required to be maintained on the farm.Similarly problems arise in existing systems when a client is part of afarm. The technique described above may also be used by the client toprovide a license to the service to use on its reply so that any clientfarm member can service the message.

Security credentials may be passed between components or services usingthe simple object access protocol SOAP. In one embodiment of theinvention, credentials, such as licenses, may be passed with SOAPmessages by including them in a SOAP “credentials” header. The headermay allow for any type of credential to be passed. Message integrity canbe associated with SOAP messages by including digital signatures orother integrity mechanisms in a SOAP “integrity” header. For example,this header can contain XML Signatures as defined in the W3C standard.Message confidentiality can be achieved by associating an XML tagencryption technology with SOAP messages. One such scheme is the XMLEncryption standard as defined by the W3C. Confidentiality of messageattachments may be achieved by including a manifest (and encryptionmeta-data) of the encrypted attachments in a SOAP “confidentiality”header.

1. A method of transmitting a message between a first party and a secondparty, the method including: receiving from the first party a messageaddressed to the second party, wherein the message is transported with afirst transport and formatted in accordance with a first protocol;determining a transport and protocol required by the second party from asecurity policy; and transmitting the message to the second party usingthe transport and protocol required by the second party.
 2. The methodof claim 1, wherein: the security policy identifies components of thesecurity system.
 3. The method of claim 1, wherein: the security policyidentifies access rights of the security system.
 4. The method of claim1, wherein: the security policy language comprises the extensible markuplanguage.
 5. The method of claim 1, wherein: the security policy isconfigurable.
 6. The method of claim 1, wherein: the security policylanguage comprises at least some logic-based components.
 7. The methodof claim 1, wherein: the security policy language comprises at leastsome rule-based components.
 8. The method of claim 1, wherein: thesecurity policy language comprises procedural components.
 9. The methodof claim 1, wherein the security policy includes an identity service.10. The method of claim 1, wherein the security policy includes anadmission service.
 11. The method of claim 1, wherein the securitypolicy includes a permission service.
 12. The method of claim 1, whereinthe security policy includes a revocation service.
 13. The method ofclaim 1, wherein the security policy includes a mapping of entities torights.
 14. The method of claim 13, wherein the security policy furtherincludes a mapping of entities to capabilities.